The present work begins with the observation of the particular relevance that has the arbitral agreement for the arbitration law, along with the affirmation of the negotiation character of this one. Next, one analyzes the subject of the formal freedom of the agreement and the diverse types of formalization of this: by reference, unidocumental and pluridocumental. Soon, the subject of the capacity for the subscription of the agreement is approached, mainly fixed to that of enjoyment and exercise, for next dealing with the requirement the necessary expression in the arbitral agreement of the manifestation it express and unequivocal of the parts to put under arbitration the controversy available, as well as that of the determination of the own controversy submissive the procedural resolution of the arbitration. Later, the assumptions of pathological arbitral agreement are analyzed, between which they are observed the non—existent arbitral agreement, the null arbitral agreement, revocable and that caducity. Soon, the scope of facultative extension of the arbitral agreement is analyzed, which affects, coverall, to the designation of the referees and the fixation of the procedure rules. Next, the effects of the arbitral agreement study, as much that positive call that it concerns the obligation of the parts to put under arbitration the controversy and to fulfill the decision of the referees, like also that denominated negative consisting of the prohibition to the static jurisdiction to know such controversies. Finally, we as much analyzed the resignation to the arbitral agreement in its modalities of express as tacit.